1. Field of the Invention
The present invention relates to an apparatus for regulating a leading end stacked position in a stacker for successively stacking thin sheet materials.
2. Description of the Related Art
Conventionally, as an example of stackers for successively stacking sheet-like articles one upon another, the one of a type in which sheet-like articles are successively introduced by means of various kinds of conveyers such as a stab conveyer, a suction conveyer and the like, into a stacker body, and then, they are forcibly or freely dropped obliquely and stacked one upon another, allowing the sheet-like articles to directly abut, at their leading ends, against a stationary ruler located at a predetermined leading end stacking position, so as to regulate the leading end stacked positions of the stacked sheet-like articles at a substantially uniform position has been well-known and it has an extremely simple structure, having a reasonable degree of stacking efficiency.
However, a sheet-like material can directly abut the stationary ruler, provided that stiff plate-like articles such as plywood or synthetic resin plates are introduced at low speeds into a stacker. Should plate-like articles or the like which are even stiff more or less be introduced into the stacker at high speeds, or should weak sheet materials as the plate-like articles be introduced into the stacker (the conveyance of veneers in a direction perpendicular to the fiber thereof can be exemplified), a fatal problem such as damage to the leading end of a plate-like article or buckling of the intermediate part thereof would be likely to occur. Accordingly, it is difficult to stack the weak plate-like articles one upon another with the use of the above-mentioned system.
Further, there is another well-known system in which a movable ruler that is held by a resilient member such as a spring so as to be resiliently displaceable, instead of the stationary ruler in the above-mentioned system, in order to buffer and absorb a shock caused by impingement of a plate-like article upon the movable ruler through extension and retraction of the spring, and after the plate-like article is once dropped to a position downstream of a predetermined stacking position, the plate-like article is moved again in a direction reverse to the direction of introduction of the plate-like article by the resilient force of the above-mentioned resilient member so as to regulate the leading end stacked positions of plate-like articles which are therefore maintained so as to be substantially uniform. This improved system is excellent in high speed responsiveness, and reduces the possibility of occurrence of a fatal problem caused by an inclination of the posture of a plate-like article upon conveyance, so as to be relatively effective in comparison with the aforementioned embodiment.
However, in order to move again the once dropped plate-like article in a direction reverse to the direction of introduction of the article as mentioned above, it is required to enable the plate-like articles to smoothly slide one upon another. However, if the plate-like articles are weak thin sheet materials, no sufficient force can be transmitted satisfactorily from the front end to the rear end thereof so as to induce a problem such that the front end part or the intermediate part of a thin sheet material to be again moved is buckled. Thus, even with the improved system, it is difficult to stack the sheet materials one upon another. As a result, either the conveyance of the sheet materials has to be once stopped each time when a sheet material is vertically dropped fop stacking by neglecting a decrease in the stacking efficiency, or they are randomly stacked without regulating the positions thereof. However, it has been practically unreasonable either.